FIG. 1 illustrates a conventional vehicle lamp 9 for mounting to a motorcycle. The conventional vehicle lamp 9 includes a housing 91 and two left-right spaced-apart lighting units 92 disposed in the housing 91. A distance (d) between boundaries of light-emitting areas of the two lighting units 92 is generally greater than 75 mm. According to Economic Commission for Europe (ECE) regulations, because the distance (d) is greater than 75 mm, each lighting unit 92 is regarded as an individual vehicle lamp. In an optical test, each lighting unit 92 is independently activated and tested to examine whether or not the requirements of Class D headlamp according to the ECE regulations can be fulfilled. Because each lighting unit 92 must overcome the test, high precision optical design and high precision manufacturing operations are needed for each lighting unit 92, thereby increasing manufacturing complexity and cost.
Based on the ECE regulations, if the distance (d) between the boundaries of the light-emitting areas of the two lighting units 92 is smaller than 75 mm, the two lighting units 92 can be declared as a single lamp, and thus can be simultaneously activated to test whether or not the two lighting units 92 put together can fulfill the requirements of Class D headlamps. As the two lighting units 92 need not be separately and singly tested, it is advantageous to reduce design complexity and fabrication costs. Thus, it is desirable to reduce the distance between the boundaries of the light emitting areas of the two lighting units 92 for enabling the two lighting units to be regarded as a single lamp, while still allowing the distance between the two lighting units 92 to maintain unchanged.